Method of making mono-chloramine



Patented Mar. 15, 1 932v J UNITED:- STATES PATENT orncs JOHN 0. BAKER, OF1MONTGLATIQ, AND FRANZlCJSCHMEL-KES, OF'IBLOOMFIELD,' NEW JERSEY, ASSIGNORS TO I WALLACE &'TIER'NAI\T rnonno'rsinc, or JERSEY, A CORPORATION on NEW JERsEx BELLEVILLE, NEW

METHODQOF G 'MQNO-CBILORAMTNE No Drawing.

This invention relates to methods of making mono-chloramine or mixtures of monoand di-chloramine containing large proportions of the former, especially dilute solutions for use in the sterilization of water. .c

When solutions containing available chlorine react with 1 solutions containing; ammonia or ammonium salts,the resulting productmay be nitrogen tri-chloride (NCldichloramine (NI-I01 or mono-chloramine (NH Cl). As to which pounds are formed by the reaction of the two solutions, can be determined and controlled by the regulation of the hydrogen ion concentration of the resulting mixture. In case-the solution is more acid than pH 4.4,mtrogen tri-chloride is formed almost quantitatively,

and if more alkaline l than pH 8.5, monochloramine is formed substantially exclusively. At hydrogen ion concentrations within the range of 4,4 to 8.5, varying proportions of di-chloramine and I monochloramine are formed. -AtpH 7 .0' (neutral point) the proportion is about of the mono-compoun to 45% of the di-chloramine.

Mono-chloramine ismuc'h slower in its sterilizing action than di-chloramine, but for numerous uses, such, for example, as swimmingpools, speed of action of the reagent when added to the water is not so essential as simplicity of preparation of the solution of the reagent to be added to the water, In

the latter respect mono-chloramine is superior as the pH does not have to be controlled within such narrow lim1ts, 7

Control of the pH involves not merely adjusting. the initial'pH, but also providing means for maintaining such pH throughout the reaction. This is necessary since, except -when ammonia and hypochlorous acid are used, the formation of "either NHClg or NH Gl results inthe liberation of acid. This will be clear from the following illustrative reactions: V a

(1) NH +HOGl=NH Cl+H O V (3) NH Cl+HOGl=NHCl+H O+HGl Application filed may 20, 1931.

formed exclusively during of these three com d the latter substance,

"following ing tank.

Serial in. 538,868.

Therefore, unless the pH is controlled when ammonium salts are used, the pH rapidly decreases so that, while mono-chloramine may .be formed at first, the solution rapidly becomes lso' acid that nitrogen tri-chloride is V the latter part. of is the reaction; While this change in pH may be avoided by the use of ammonia and hypochlorous acid, such isolutionof the problem is notide sirable since ammonia is much lesscon- .ven'ientand far more dangerous to handle than ammonium salts.

, f One of the ob ects, therefore, of the present lnvention is to provldea simple, cheap method of absorbing the acid formed when ammon um salts are employed in the manufacture of mono-chloramine. I 7

We have found that-the acid formed can be very easily and cheaply absorbed and the pH kept within the range over which the mono-chloramine is the preponderating product by the use of bases, especially substan tially insolublebases, such as calcium carbonate. Thereaction involved, when using is approximately the (5) 263,00 2nc1=-cac12+ca nco;)2

While the reaction (4) produces twice as much acid as reaction (3), the advantage of hypochlorous acid over chlorine in this respect is more apparent than real,;since cal cium carbonate is required to form hypochlorous acid from chlorine. c

.' GaCl +2HOGl+Ga(HCO3)2 The same total amount of calcium carbonate is required whether theentire reactiontakes place by'reactions" (6), (8) and (5,), or by reactions (4;) and; (5)

The simplest method of. carrying out-the i:

process is to ammonium salt with calcium carbonate and then add the mixture as a unit to the treat- A' zdesirabl'e mixture to use has the following composition: 19% NH Gl; 81% CaGO ith this proportion, assumingall ingredients to bechemi ally pure, -the ammonium mix ammonium chloride on other a ice chloride is slightly in excess ofthat'called gen tri-chloride excess of that required or reaction (2). The calcium carbonate is about 12 to over that required to absorb all the hydrochloric acid per reaction (5). In general, the ammonium-salt and the calcium carbonate are mixed in. about the ratio of one unit of NIL CaCO the latter preferably being in slight forbysuch ratio. This mixture is used in the proportion of 4 pounds to each 1 pound of chlorine used in reaction (4). As solutions oi"chlorine gas have a pH within the range in which nitrois formed, we prefer-to add chlorine gas or a solution of chlorine gasto a solution of ammonium salt instead of adding the latter dry orin solution to a solution of chlorine, although both procedures may be-used with goodresults. As mono-chloramine is more stable in dilutethan in con centrated solutions, the reacting solution should ordinarily not contain much over 0.2%; chlorine and preferably about 0.1%.

A suitable procedure is to agitate 0.4 pounds of the mixture of ammonium chloride and calcium carbonate with each 100 pounds of water used, to dissolve the ammonium chloride, and then add to each such solution 0.1 pound Suitable stirringor agitating means may be provided to disseminate the insoluble carbonate powder in the solution while the chlorine. is being added thereto. Suitable means may be employed for settling any excess carbonate out of the solution before the latter is discharged to the point of use.

Vhile ammonium chloride and calcium carbonate have been mentioned as convenient substances .to employ, theinvention is not limited thereto. Other salts of ammonium may be employed, such as the sulphate. Similarly, other substantially insoluble bases may be used, such as magnesium carbonate. The latter compound, or mixtures of calcium and magnesium carbonate such as dolomite, are much slower to react with acid than calcium carbonate and, hence, are less desirable. What is claimed is: l. The process of making mono-chloramine, which comprises causing available chlorineto react on ammoniacal material in the presence of a weak base adapted and in quantity suflicient to absorb all the acid liberated by said reaction. i

2. The process as in claim base consists principally insoluble basic material. 3. The process as in claim 1, in 'which the base is principally calcium carbonate.

he process or" making mono-chlor amine, which comprises adding a mixture of 1, in which the an ammonium salt and a substantially insoluble base to able chlorine, the in excess of that a solution containing availamount of base added being required to absorb'all the to each two units of of a substantially acid liberated by the reaction between the ammonium salt and the available chlorine.

5. The process as in claim 4:, in which the base is principally calcium carbonate.

he process of making mono-chloramine, which comprises adding a mixture of about 19% ammonium chloride and 81% calcium carbonate to a solution of chlorine.

he, process of making mono-chloramine as in claim 6, in which the mixture is added tochlorine in the ratio of about 4 pounds of the mixture to each 1 pound of chlorine.

8..:The process of making mono-chloramine, which comprises causing chlorine to react on an ammonium salt in about StOlChlOr metrical proportions, in the presence of calcium carbonate in excess of the amount required to absorb the acid liberated by such reaction with the formation of calcium bif carbonate.

9. The process of making mono-chloraminc, which'comprises adding a mixture of ammonium salt and calcium carbonate to a solution of chlorine, the proportion of ammonium salt to calcium carbonate being slightly less than the ratio of one unit of 4 to each two units of (la-CO and the proportion of ammonium salt to chlorine being about in the ratio of one unit of NH to each unit of C1 v i 10. The process of makingmono-chloramine,which comprises mixing an ammonium salt and a base with water and then adding chlorine thereto, the amount of base added being sufficient to absorb all the acid liberated by the reaction between the ammonium salt and the chlorine.

In testimony whereof, we have hereunto set our hands.

JOHN C. BAKER. FRANZ C. SCHMELKES. 

